A mixer for an exhaust system of an internal combustion engine, which is used to mix and evaporate a reducing agent with an exhaust gas flow, is known from DE 10 2007 028 449 A1. The mixer has for this purpose a pipe section, which borders a flow cross section, through which the exhaust gas flow can flow, in a circumferential direction, and which extends in an axial direction from a first or incoming flow-side axial side of the pipe section to a second or discharge-side axial side of the pipe section. Furthermore, the pipe section comprises a plurality of guide blades, which project from the pipe section on one of the axial sides, doing so such that they protrude into the flow cross section. The guide blades project essentially radially from the pipe section in the prior-art mixer. Further, all guide blades are arranged on the same axial side of the pipe section in the prior-art mixer. Furthermore, all guide blades are set with the same pitch angle in relation to the axial direction in the prior-art mixer. As a result, the exhaust gas flow is affected in case of a twist concentrically to the central longitudinal axis of the mixer during its flow through the mixer.
It is often necessary in exhaust systems of internal combustion engines to introduce a reactant, i.e., preferably an oxidizing agent or a reducing agent, into the exhaust gas flow. For example, a fuel may be introduced as an oxidizing agent upstream of an oxidation catalytic converter in order to increase the heat in the exhaust gas flow by a catalytic reaction of the fuel in the oxidation catalytic converter. For example, a particle filter can be heated in this manner to a regeneration temperature. Further, it is known in connection with so-called SCR systems that an aqueous urea solution may be introduced as a reducing agent into the exhaust gas flow upstream of an SCR catalytic converter in order to bring about a reduction of nitrogen oxides in the SCR catalytic converter. SCR denotes Selective Catalytic Reduction. The mixing of the reactant introduced with the exhaust gas flow can be improved by means of such a mixer. In addition, the mixer may act as an evaporator and prevent liquid reactant from reaching the respective catalytic converter in case of liquid reactants.